In situ grazing on plankton 10 µm by the boreal sponge Mycale lingua

Abstract

Ultraplankton, heterotrophic and autotrophic plankton c5 pm, are the most abundant food source in the world's oceans, yet their role as a food source for macroinvertebrates is largely unexamined.We quantified in situ feeding on heterotrophic and autotrophic plankton < l 0 pm by the boreal sponge Mycale l ~n g u a using measurements that quantified sponge feeding effic~enc~es, pumping rates, and abundance to determine the c o n t r ~b u t ~o n of plankton < l 0 pm to sponge carbon Intake.Using dualbeam flow cytometry we identified 5 populations of plankton c10 pm: heterotrophic bactena.Prochlorococcus, Synechococcus-type cyanobacteria, autotrophic eucaryotes <3 pm, and autotrophic eucaryotes 3 to 10 pm.Mycale lingua nonselectively grazed on all types of plankton < l 0 pm.Prochlorococcus was filtered with the highest efficiency (93%), followed by Synechococcus-type cyanobacteria (89%), autotrophic eucaryotes 3 to 10 I.lm (86":,), heterotrophic bacteria (74 %), and autotrophic eucaryotes c 3 pm (72%).We conservatively estimate that M. linqua at naturally occurring denslties can obtain 29 mg C d-' m-' feeding on plankton c10 pm, w ~t h 74% resulting from ultraplankton, suggestlng that ultraplankton are an important overlooked component of benthic-pelag~c coupling.